Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells. This depolarization then causes adjacent locations to similarly depolarize. The impulse travels down the axon in one direction only, to the axon terminal where it signals other neurons.Īn action potential occurs when the membrane potential of a specific cell rapidly rises and falls. Repolarization occurs when K + channels open and K + moves out of the axon, creating a change in electric polarity between the outside of the cell and the inside. Na + channels open at the beginning of the action potential, and Na + moves into the axon, causing depolarization. In response to a signal from another neuron, sodium- (Na +) and potassium- (K +)–gated ion channels open and close as the membrane reaches its threshold potential. As an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon.
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